minor #10637 Update IsTrue.rst (u-mulder)

This PR was merged into the 2.8 branch.

Discussion
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Update IsTrue.rst

Correct class names for Validator and Constraint classes for `IsTrue` is `IsTrue` (not just `True`).

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Commits
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81ba832 Update IsTrue.rst

Author: javiereguiluz

reference/constraints/IsTrue.rst

@@ -13,9 +13,9 @@ Also see :doc:`IsFalse <IsFalse>`.
 | Options        | - `message`_                                                        |
 |                | - `payload`_                                                        |
 +----------------+---------------------------------------------------------------------+
-| Class          | :class:`Symfony\\Component\\Validator\\Constraints\\True`           |
+| Class          | :class:`Symfony\\Component\\Validator\\Constraints\\IsTrue`         |
 +----------------+---------------------------------------------------------------------+
-| Validator      | :class:`Symfony\\Component\\Validator\\Constraints\\TrueValidator`  |
+| Validator      | :class:`Symfony\\Component\\Validator\\Constraints\\IsTrueValidator`|
 +----------------+---------------------------------------------------------------------+
 
 Basic Usage